Power consumption has become a primary concern within many electronic systems, especially in portable devices running from a battery. These devices can include numerous subsystems often being connected or disconnected through switching elements to save power. Today, and in most systems, electronic devices use analog switches or low dropout regulators (LDOs). The subsystems, through these switching elements, can be connected to a DC/DC converter. Often these DC/DC converters include load lines and variable output voltages which attempt to maximize battery life.
However, by connecting the switching elements to a DC/DC converter, noise can be introduced to the load potentially interfering with downstream components, including RF components. For analog switches, many systems have utilized LC filters to attenuate this noise. If an LDO is used, instead of an analog switch, and the LDO filtering response is not sufficient, many systems also utilize passive filter components in addition to an LDO for filtering.
The use of an analog switch is non-ideal since passive filter components must be added taking up board space and raising the overall cost of the system. In addition, the use of an LDO as a filtering element, whether with or without external components, is non-ideal since LDOs generally have a constant output voltage that does not track the input. Typically, this produces a greater voltage drop and in essence, a lower efficiency than ideal until right before dropout. Furthermore, it is prohibitive to provide a multi-order wideband filter response utilizing either of the above solutions due to component proliferation and the single order response generally provided by LDOs.